Effects of Peanut Stand Uniformity and Herbicide Regime on Weed Management and Yield.

Crop stand directly affects ability of any crop to compete with weeds. To capture this form of cultural weed control, final crop stands need to be uniform. Peanut stands are frequently non-uniform, despite the use of precision vacuum planters. Trials were conducted from 2009 through 2011 in Tifton, GA to determine the effect of non-uniform peanut stands on weed control, grade, and marketable peanut yield. Non-uniform peanut stands were established by modifying vacuum planter discs that created skips 18 cm wide and 36 cm wide at regular intervals and compared with peanut at a uniform stand. The weed control regimes chosen reflected differing degrees of residual weed control provided by flumioxazin or imazapic and addressed the need for residual weed control when peanut stands are non-uniform. Postemergence (POST) herbicides bentazon, paraquat, and 2,4-DB were chosen to test the theory that properly timed applications of non-residual herbicides will control weeds in skips without the need for preemergence (PRE) herbicides. There was no significant interaction between peanut stand uniformity and weed control regime for any parameter. Weed response to peanut stand was variable among species and inconsistent. Weed densities tended to be lower when the residual herbicides flumioxazin and/or imazapic were part of the herbicide regime. Peanut yields and percent total sound mature kernels were not affected by narrow (18 cm) skips, but were reduced two years out of three by wide (36 cm) skips. Peanut yields and grade were similar among weed control regimes that used PRE herbicides and POST herbicides with no residual weed control properties. These results indicate that weed control considerations are not a factor when peanut skips are <18 cm. The herbicide choices evaluated are capable of controlling weeds allowing peanut to compensate for non-uniform stands and not have yield reduction when skips are <18 cm. [ABSTRACT FROM AUTHOR]